This invention relates generally to AC welding machines or the like and more particularly to the design and colling methods directed to power transformers requiring high current low voltage outputs.
Transformers and other high current devices such as those used for AC welding and other power applications include transformers, resistors, solid state electronic devices and the like which transform, control and regulate output voltage at current levels required for various purposes.
These various electrical and electronic components become excessively hot during normal operation due to their internal electrical resistance. These internal losses especially in AC welding machines are at such high levels that these devices must be turned off during periods of operation due to overheating. If cooling is insufficient and excessive heating occurs, failure of the device will generally result which requires repair and/or replacement of the device.
Presently, the cooling of such devices of this type is fan provided air which is directed in a wide pattern toward the entire operating device. This type of cooling has been found to be insufficient to maintain proper cooling for operating equipment of this type at their normally recommended operating temperatures especially for any continuous length of time. It has been found that the power supply of an average portable AC welding machine is approximately 40% efficient and even the most efficient hardly ever exceed an efficiency of 50%. This means in effect that 50% to 60% of the power consumed by the device is due to its own internal electrical resistance. This internal resistance results in internal heat when connected to an AC source even while not having an output load.
Presently available portable AC welding machines, due to these internal losses, have a duty cycle ranging from approximately 20% to 50% that is 20% to 50% of their time can be used for their intended operation and the other 80% to 50% of their time is spent in an inactive or off state while the machine is cooling. For example, the average available AC welding machine uses a very high excitation current and in some cases the machine will consume excitation power of from 500 to 1500 watts when the machine is merely energized and has no output load.
With conservation of energy and maximum utilization of equipment in mind, applicants present invention amounts to a quantum advancement in the power transformer for the portable AC welding art.